As prior art graphite particles, natural graphite particle, artificial graphite particle prepared by graphitization of coke, artificial graphite particle prepared by graphitization of organic polymeric material, pitch and the like, graphite particles prepared by pulverizing these graphites, etc. can be referred to. These graphite particles are put to use as a negative electrode for lithium secondary battery by mixing a graphite particle with an organic binder and an organic solvent to prepare a graphite paste, coating a copper foil surface with the graphite paste, and then evaporating the solvent. For instance, it is intended in JP-B 62-23433 to eliminate the problem of internal short-circuit caused by lithium dendrite and to improve the cycle characteristics by using graphite as negative electrode.
However, in the natural graphite particle in which graphite crystals are well grown and in the artificial graphites prepared by graphitization of coke, the interlaminar bonding force in the direction of c-axis of crystal is weaker than the bonding force in the crystal face direction, and therefore the bonding between graphite layers is broken upon pulverization to form the so-called “flake graphite” having a large aspect ratio. If the flake graphite particle having a great aspect ratio is kneaded together with a binder and coated onto a current collector to form an electrode, the flaky graphite particles are oriented in the plane direction of current collector. As its result, due to repeated occlusion of lithium into graphite crystal and its release, a strain arises in the direction of c-axis, which causes an internal breakage of electrode. Thus, the cycle characteristics are deterio-rated and, in addition, the rapid charge-discharge characteristics tend to become worse.
Further, prior art graphite particles having a large crystallite size in the face direction requires a long period of time for occlusion and release of lithium. Further, prior flaky graphite particles having a high aspect ratio have a great specific surface area. Thus, the lithium secondary battery obtained therefrom has a large irreversible capacity in the first cycle and, in addition, such graphite particles are poor in adhesiveness to current collector so that a large quantity of binder is needed. If the adhesiveness to current collector is not good, the current-collecting effect is not good and discharge capacity, rapid charge-discharge characteristics and cycle characteristics are deteriorated. Thus, it is desired to develop a graphite particle excellent in the rapid charge-discharge characteristics and cycle characteristics, or small in the irreversible capacity in the first cycle and excellent in cycle characteristics, or small in the irreversible capacity in the first cycle and capable of improving rapid charge-discharge characteristics and cycle characteristics, in the form of a lithium secondary battery.